A nonpolar molecule is a molecule that has no polar bonds or that has evenly distributed polar bonds, so the bond dipoles cancel each other out. A nonpolar molecule does not create a molecular dipole.
An example of a nonpolar molecule is carbon dioxide. It has polar bonds, but the electrical charges are evenly distributed, thereby canceling each other out. Some other examples of nonpolar molecules are hydrogen, nitrogen and oxygen molecules.
A polar molecule is a molecule in which the electrical charges are not evenly distributed and a net dipole is created. Water and ammonia are examples of polar molecules.